Numerous systems and methods for extinguishing fires in a building have been developed. Historically, the most common method of fire suppression has been the use of sprinkler systems to spray water into a building for cooling the fire and wetting additional fuel that the fire requires to propagate. One problem with this approach is the damage that is caused by the water to the contents of the occupied space.
The “total flood” clean agent fire protection system industry provides high value asset protection for spaces, such as computer rooms, telecommunications facilities, museums, record storage areas, and those housing power generation equipment. “Total flood” protection in such applications is provided by automatically filling the protected compartment completely at a uniform concentration that assures that the fire will be extinguished, no matter where it might be located. The extinguishing medium used in such systems is expected to be “clean”—that is, leave no or very little residue behind after discharge that must be cleaned up.
Known total flood fire protection systems typically comprise a bank of several (commonly tens or more) thick-walled metal bottles for holding an extinguishant (either liquefied or in the gaseous state) at high pressure to permit high-density storage. The extinguishant is released via either manual or automatic activation of high-strength, special purpose valves on the bottles. In order to transmit an extinguishant at masses required to meet precise extinguishing concentrations within a tight tolerance band of room concentration required to meet both the extinguishing and inhalation toxicity requirements, a complex plumbing network designed for the space is required. Furthermore, independent capacities required for individual rooms in a typical multi-room protection scenario (such as a factory or high-rise building) using the same distribution network must be accounted for. Such design and corresponding installation work, including development of flow calculation methodologies for complex flow considerations, requires considerable up-front effort and expense.
High-pressure bottles require frequent inspection due to their propensity for leaks. Once a leak is identified, the leaking bottle may need to be sent to a central re-filling installation, resulting in protection down time at the customer site. Such down time can also be experienced in the event of a man-made or natural disaster, such as a gas leak explosion, tornado or earthquake, which can also damage the piping network itself.
The fluorocarbon known as Halon 1301 has been used in “total flood” systems because it is clean, somewhat non-toxic and highly efficient. Due to their use of ozone depleting greenhouse gases, however, systems employing Halon 1301 are being replaced by more environmentally friendly alternative systems, as mandated by the 1987 Montreal and 1997 Kyoto International Protocols. One example of a Halon 1301 alternative system uses the hydroflourocarbon HFC-227ea (e.g. Marketed as “FM-200” or “FE-227” in Fire Suppression Systems such as those manufactured by Kidde Fire Systems).
Such “first generation” Halon alternatives, including “clean” hydrofluorocarbons behave in a similar manner to Halon 1301, but have been found not to be as effective in comparison since they typically do not have the flame chemistry inhibition of Halon 1301. As a result, fire suppression systems using Halon replacements require from two to ten times the extinguishant mass and storage space, and are therefore more costly. Furthermore, the increased storage space required for the large increase in number of extinguishant bottles poses a difficult placement problem for facility engineers, and a considerable obstacle for those wishing to retrofit an existing Halon installation with a bottle “farm” many times bigger than its Halon predecessor in a limited storage space.
Most of these Halon alternative hydrofluorocarbons have human exposure toxicity limits very close to their required extinguishing design concentrations. They are therefore more sensitive to changes in room storage filling capacity in terms of occupant risk. Such exposure times are typically limited to five minute or less providing occupants with reduced evacuation capability. Occupants who are injured, aged, disabled and may also be medical patients may find this evacuation time challenging, and the increased cardio toxicity risk with many of these Halon alternative extinguishants makes limited exposure scenarios even more critical.
Once discharged into a room, known Halon alternatives of this type are hydrofluorocarbons having a propensity to decompose into large quantities of hydrogen fluoride, after exposure to an open flame. Hydrogen fluoride is an acid that can pose significant health hazards to occupants and rescue personnel, and can damage equipment. For this reason, at least the U.S. Navy has used water mist to wash out hydrofluoric acid after hydrofluorocarbon (“HFC”) discharge in a machinery space fire, in addition to cooling the compartments, to protect firefighter personnel. Furthermore, HFC chemicals have been determined to have long atmospheric lifetimes, thereby making them subject to subsequent global warming legislation worldwide in line with the Kyoto Protocol Treaty and proposed November 2009 changes to the Montreal Protocol Treaty. Also, the California Environmental Protection Agency's, Assembly Bill 32, the global warming solutions act of 2006, bans the eventual use of HFC's in fire systems.
“Environmentally friendly” alternatives to the hydrofluorocarbons have been proposed and even fielded to a limited degree, but many also suffer from their own design and operational limitations. Water mist systems were devised to use less water than sprinkler systems, and hence cause less water-related damage, although such damage is only reduced, not eliminated. Even with considerable research and engineering expertise applied internationally, it has proven very difficult to design mist delivery systems for fire suppression around obstacles that are as effective as gases. The efficiency of suppression is largely influenced by the size and nature of the fire. Inert gas systems, such as those using nitrogen or argon, require up to ten times the number of bottles of their Halon predecessor (due to their inefficiency and inability to be liquefied under pressure in a practical manner). Such requires not only considerable additional storage space, but often larger diameter plumbing that would need to replace Halon-suitable pipes. The very high pressure bottles used in inert gas systems can also pose an additional safety hazard if damaged or otherwise compromised, including the thicker-walled distribution plumbing that might be vulnerable at any joint connections.
Another method for fire suppression involves dispersal of gases such as nitrogen, in order to displace oxygen in an enclosed space and thereby terminate a fire while still rendering the enclosed space safe for human occupancy for a period of time. For example, U.S. Pat. No. 4,601,344, issued to The Secretary of the Navy, discloses a method of using a glycidyl azide polymer composition and a high nitrogen solid additive to generate nitrogen gas for use in suppressing fires. This patent envisions delivery of a generated gas to a fire via pipes and ducts, and does not disclose any particular means by which to package the solid additive. Furthermore, the patent does not consider the challenges in distributing an appropriate quantity of generated nitrogen gas into a habitable space and does not to consider concentrations that would reliably extinguish fires, while permitting the safe occupancy and exposure to humans for a time.
According to the requirements for inert gas generator fire suppression systems inside a normally occupied space set by the National Fire Protection Association (NFPA) such as NFPA Standard 2001, the US United States Environment Protection Agency (EPA) such as the SNAP List, and UL/FM/ULC Listings & Approvals, a space must be able to be occupied for up to five (5) minutes. Furthermore, inert gases must be reduced to a maximum of 75 degrees Celsius or 167 degrees Fahrenheit at the generator's discharge port.
U.S. Pat. Nos. 6,016,874 and 6,257,341 (Bennett) disclose the use of a dischargeable container having self-contained therein an inert gas composition. A discharge valve controls the flow of the gas composition from the closed container into a conduit. A solid propellant is ignited by an electric squib and burns thereby generating nitrogen gas. This patent envisions delivery of a generated gas via a conduit into a space.
U.S. Pat. No. 7,028,782 (Richardson) and U.S. Patent Application Publication No. 2005/0189123 (Richardson et al.) disclose means of exploiting gas generator technology by use of non-azide propellants in a stand-alone system featuring multiple individual gas generator cartridges in a given container. Some non-azide materials produce water vapor, however, which can condense onto the walls and other surfaces of the compartment to be protected. Some end users prefer protection schemes that pose little or no possibility of any such water condensation that might harm paper records or other moisture-sensitive contents. Furthermore, the extinguishant from non-azide materials is typically extremely hot, and therefore must be cooled significantly for use in normally occupied spaces. Cooling is achieved with the use of a large mass of cooling bed material also stored in proximity to the multi-cartridge container. The large mass takes up space that could be filled with additional generators, thereby reducing the overall protection space efficiency of a given cartridge container.
Although systems exist for total flood fire suppression applications, improvements are of course desirable. It is an object of the present invention to provide a device and method for delivering a fire suppressing gas into a space.